Huge tunneling machine off to painfully slow start

Originally published August 28, 2013 at 11:21 am

Updated August 28, 2013 at 9:17 pm

An Aug. 13 aerial view of the site where tunnel-boring machine Bertha is at work shows that progress has been slow since digging began on July 30. According to the state Department of Transportation website, the machine was slowed by a 15-foot-thick wall of concrete, which it broke through last week.

This aerial view from Aug. 20 shows the site where tunnel-boring machine Bertha is at work near the Alaskan Way Viaduct. Bertha is working on a new tunnel route for Highway 99 through downtown Seattle to replace the viaduct.

After nearly a month on the job, Seattle’s giant highway tunneling machine has advanced a mere 24 feet.

Contractors blame the delays mostly on fiberglass strands that became stuck near the cutting face of the drill. That problem is solved, but now a labor dispute has interrupted the excavation along Seattle’s waterfront, said Chris Dixon, project director for the Seattle Tunnel Partners team.

The pace is about two weeks behind what the team expected.

Before drilling began, state officials estimated it would progress at 6 feet per day to start, and eventually accelerate to 35 feet per day in good soil under downtown.

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The 1.7-mile dig is supposed to be finished by fall 2014, and the new Highway 99 tunnel to open for traffic at the end of 2015.

Officials say they aren’t worried, at this early stage, about missing the schedule.

The project’s 250 workers, at the launch pit in Sodo, are still performing tasks such as putting the arc-shaped tunnel segments into position, and adjusting the drill, Dixon said, even though the machine known as Bertha wasn’t eating dirt Tuesday.

“We’re not laying off, we’ve shortened some shifts and are canceling some others,” he said.

After the July 30 start, bunches of fiberglass strands, 2 feet long and as much as an inch thick, began to clump at the bottom of the machine, just behind the cutting face, Dixon said.

That spot is where the dirt is scooped up by a red screw conveyor that spins within a big tube, nudging the soil toward the rear of the machine — where it’s dropped onto a conveyor belt headed to Terminal 46.

Fiberglass jammed the screw.

Contractors anticipated some difficulty, but the fiberglass caused more trouble than expected. Bertha has bigger openings in the cutter head than most drills, so it didn’t chew the fiberglass into manageable pieces, Dixon said.

Workers removed the strands by spraying them with high-pressure water jets, which knocked concrete pebbles off the fiberglass, loosening the bundles.

This fiberglass was embedded in the front wall, to add strength, when the concrete was poured to build the pit. Steel rebar usually plays this role in other concrete walls, but a tunnel machine cannot cut through steel. Bertha’s cutters are beyond the fiberglass now.

The drill will next move through 100 feet of soil mixed with concrete grout, which must be removed by truck. Then it will reach cleaner soil that can be barged to a quarry near Port Townsend.

Dixon said the job will stay on track if the labor dispute ends soon with the International Longshore and Warehouse Union (ILWU), which is picketing at Terminal 46.

The longshore union is demanding four waterfront jobs — to run a soil-conveyor belt, drive a front-end loader, and position the barges using two people. The contractors instead hired building-trades workers from another union.

For several days, the tunnel contractors have not sent workers to cross the picket line so that material can be trucked away.

And if dirt doesn’t move, neither does Bertha.

Officials for the building trades filed a complaint last week to the National Labor Relations Board, to oppose the ILWU action. Tunnel managers hope for a ruling within days.

Cam Williams, president of ILWU Local 19 in Seattle, said the union hasn’t decided yet how it would respond if the labor board rules against the longshore workers.

He attributed Bertha’s slow pace to “technical problems” rather than a labor standoff.

Dixon said the delays can be overcome.

“The machine’s working well,” he said. “We were able to launch it successfully, the ring builds are going well. It’s all coming together. There’s no operational issues that have surfaced.”

Meanwhile, the state published a reminder of how much progress has been made, through time-lapse video of the last two years. A dirt lot in Sodo was transformed into the starting blocks for the world’s widest drill, at 57 feet, 4 inches diameter.

Seattle transportation officials expect a slow start, said spokesman Rick Sheridan. “WashDOT has always been clear to us that this is a period of testing, staff instruction, and process refinement,” he said.

The $2 billion tunnel is the most difficult segment of the state’s $3.1 billion replacement for the 1950s Alaskan Way Viaduct, which is at risk of failure in a severe earthquake.